1. Field of the Invention
The present invention relates to a method and apparatus for detecting contraband materials. More specifically, the present invention relates to a method and apparatus for non-destructive testing of objects for the purpose of detecting contraband materials.
2. Description of the Related Art
Current attempts at providing devices and methods for detecting contraband materials stored inside objects such as vehicles, luggage, or cargo containers have resulted in the development of technology that is inadequate to reliably screen a large number of such objects while maintaining high sensitivity for the detection of contraband materials. Existing screening techniques for detection of contraband materials are subject to a number of inefficiencies that decrease the reliability of the screening process and increase the possibility of contraband materials advancing undetected past a security checkpoint.
There exists no simple way to detect and deter the threat of contraband materials contained within vehicles, luggage, or cargo shipping containers. In order to assure that no contraband materials advance past a security checkpoint, each object must be screened for the presence of contraband materials. Various technologies have been developed for detecting a multitude of different contraband materials, including chemical, biological, radiological, nuclear, explosive, and narcotics materials. The procedure of scanning every object at a security checkpoint is effective in reliably screening for a variety of contraband materials; however, existing screening limitations prohibitively increase inspection costs and slow down the inspection process.
In order to screen objects for contraband materials in a cost-effective and time-efficient manner, generally only a portion of the objects passing through security checkpoints are examined. Inherent technological limitations in terms of size and/or volume of objects that can be screened are the main cause for the flaws in existing screening systems and methods. Considering the large volume of objects passing every day through various security checkpoints, and various locations, including border entry points, busy airports, and commercial and government buildings, remain vulnerable against the possibility of contraband materials passing undetected. Most objects passing through such locations are not checked for the presence of contraband materials, including explosives, biological, chemical, nuclear, or other destructive elements or devices.
One of the most common methods of screening objects for the presence of contraband materials involves the use of handheld devices. Such devices are generally used by security personnel to screen limited areas of vehicles, luggage, or cargo containers. These handheld devices are of limited use because they cannot be used to scan the entire area inside and outside vehicles, luggage, or cargo containers. Other screening methods involve visual inspections wherein security personnel visually inspect the object for the presence of contraband materials. Visual inspection may be further aided by the use of specially-trained dogs or handheld equipment having one or more sensors for detecting various contraband materials. One of the main disadvantages of these methods is that they are of very limited use when a large number of objects must be screened.
Various devices and methods for contraband detection may utilize X-ray technology to scan the interior of objects, such as vehicles, luggage, or cargo containers. Typically, these devices and methods utilize passive detection technology or active X-ray technology. In passive detection devices, no source of X-ray or gamma ray is projected towards the object. Passive detection devices are capable of detecting radiation emanating from radiological material such as uranium or plutonium concealed inside an object by detecting radiation emitted from such material. Despite their widespread use, passive detection devices are associated with the problem of unreliable detection. Passive detectors are commonly known to provide false detections from ordinary materials, such as ceramics, which are known to emit slight radiation.
In active X-ray devices, a source projects X-ray or gamma ray radiation which passes through an object. The radiation is detected by an array of detectors located on the opposing side of the object. Detectors measure the change in radiation and determine the presence of contraband materials concealed inside the object based on the change of radiation characteristics. Active X-ray devices are complex and require large radiation sources and detector arrays for scanning large objects, such as vehicles and cargo containers.
While conventional X-ray technology speeds up the inspection process by not requiring that each object be opened and visually inspected, it is associated with a number of disadvantages. Existing devices that utilize passive screening technology are susceptible to generating false alarms. Additionally, they are of limited use when radiological or nuclear material is concealed inside thick shields which do not allow the passage of X-rays. Although powerful active X-ray devices capable of generating X-rays which penetrate through thick materials, such as vehicles or shipping containers, exist in the prior art, these devices are prohibitively large and heavy to be used in any setting that is not in a fixed location on the ground. Additionally, they present a radiation exposure hazard to personnel surrounding such devices.
There exist various devices and methods for ground-based inspection of objects for the presence of contraband materials. U.S. Pat. No. 5,065,418 to Bermbach et al. suggests an apparatus for inspecting containers or vehicles at airports for illegal contents. Similarly, U.S. Pat. No. 5,764,683 to Swift et al. and U.S. Pat. No. 5,638,420 to Armistead disclose devices for inspecting objects, such as motor vehicles or freight pallets, wherein the device has a movable frame which can straddle the object being inspected. These approaches suggest a secondary operation that must be performed on the ground, thereby increasing the inefficiencies of the port's operations. U.S. Pat. No. 7,216,548 to Kurita et al. suggests improvements for the straddle-based inspection device with the incorporation of a position control system which helps to position the inspection device at the container location; however, such a device does not address the main concern of having a secondary operation that must be performed while the container is on the ground.
U.S. Pat. No. 6,058,158 to Eiler discloses an X-ray examination device for checking the contents of closed cargo carriers having two steerable single-track carriages disposed parallel to each other. One or more screened vehicles having leaded mesh screens for surrounding the cargo containers are provided to shield against harmful X-rays outside the cargo container area. The vehicle described in this patent is elaborate and large and cannot be mounted on a moving device, such as a shipyard crane. Additionally, the invention will extend the handling time and the space required to perform such secondary inspection operations. Similarly, U.S. Pat. No. 5,838,759 to Armistead describes an inspection system for detecting contraband in cargo containers, vehicles, rail cars, etc. having an X-ray source and X-ray imaging capability. This is another device for secondary inspection requiring large specialized equipment. U.S. Pat. No. 7,317,782 B2 to Bjorkholm suggests mounting of fixed X-ray radiographic devices on a crane's fixed structure, assuming the crane will lower the container between the X-ray beam source and the receptor, allowing the system to capture the radiographic image of the container. A disadvantage of this invention is that by forcing the container to be transported to a fixed X-ray scanning location, it inevitably slows down the operation of the security checkpoint. Additionally, the limited time an object spends inside the scanning location may be inadequate for producing a detailed radiographic image of the object. An additional disadvantage of many of the above-described prior art inventions is that they expose operators to dangerous X-rays while objects are being inspected.
The above-described prior art devices require a secondary procedure that is implemented in addition to the existing procedures at a security checkpoint. Therefore, the addition of a secondary procedure necessarily increases the processing time for each object that is inspected. In common security checkpoint operations, such as vehicles moving past a border entry point or cargo containers being unloaded from a shipping vessel, screening operations must be optimized to provide the most time-efficient procedure that produces reliable results. In a shipyard setting where thousands of cargo containers may be unloaded from ships, each second of cargo container processing time must be maximized to reduce inefficiencies. Arguably, the best moment for screening each cargo container is while it is being loaded or unloaded from a vessel by a bay-side crane. During this process, the container is locked to the crane's hoist mechanism and is carried from the vessel to the shore or vice-versa. Generally, it takes about 60 to 120 seconds to complete this process. During this time, the crane's hoist mechanism remains in contact with the cargo container and provides a great opportunity to screen the cargo while it is in transit. However, the prevailing detection technologies remain land-based because of the above-described limitations.
Prior art radiation measurement/detection technologies for detection of contraband materials are not amenable for use on a crane and its hoist mechanism. Due to the complexity involved in applying and adapting active X-ray sensing technology on a shipyard crane, prior art systems rely on passive detection methods. However, passive and sniffer type detectors are unreliable and are known for producing false alarms. U.S. Pat. No. 6,936,820 B2 to Peoples describes a cargo container inspection device that uses passive radiological detectors for inspection of conventional cargo containers. U.S. Pat. No. 7,116,235 B2 to Alioto et al. suggests a method for comparing the gamma ray and neutron data measured by passive detectors with the expected gamma ray and neutron count of radiological or nuclear contraband materials to determine the presence of radiological substances hidden in a cargo container. U.S. Pat. No. 7,142,109 B1 to Frank suggests an elaborate arrangement to improve the measurement performance of the passive and sniffer type sensors. However, all of the above-described devices and methods fail to provide a solution that would provide reliable detection. U.S. Pat. No. 7,808,381 B2 to Murphy et al. describes a system and method for screening inter-modal shipping containers for the presence of certain weapons. All of the above-described prior art devices and methods are associated with a number of disadvantages which do not enable their application on conventional crane systems. Additionally, the size and weight of active X-ray devices necessary for scanning large objects, such as vehicles and containers, require fixed, ground-based locations.
Accordingly, there exists a need for a method and apparatus for non-destructive testing of objects for the purpose of detecting a plurality of contraband materials which overcome the problems associated with the prior art. Additionally, there exists a need for a method and apparatus for non-destructive testing of objects that increases the efficiency of current contraband screening processes and decreases the potential for false alarms. Furthermore, an additional need exists in the art for a method and apparatus for non-destructive testing of objects which is easily adapted for use with existing devices used at a security checkpoint without requiring additional processes or steps in the screening process.